Three-subjet distributions in neutral current deep inelastic
                              scattering at HERA

                          ZEUS Collaboration

                              Abstract

Three-subjet distributions were measured in neutral current deep
inelastic ep scattering with the ZEUS detector at HERA using an
integrated luminosity of 299 pb^-1. Jets were identified using the
kt cluster algorithm in the laboratory frame. Subjets were defined
as jet-like substructures identified by a reapplication of the cluster
algorithm at a smaller value of the resolution parameter y_cut. 
Measurements of subjet distributions for jets with exactly
three subjets at y_cut = 0.01 are presented as functions of observables
sensitive to the pattern of parton radiation and to the colour
coherence between the initial and final states. Measurements are also
presented as functions of angular correlations between the three
subjets which provide a stringent test of perturbative QCD and show
sensitivity to the contributions from different colour configurations.
Perturbative QCD predictions give an adequate description of the data.